Ensuring high efficiency of thin film photovoltaic modules with inline measurement

In the manufacture of thin film solar panels or foils (e.g. CIS/CIGS, CdTe) it is crucial to maintain the specified limits of thickness and composition exactly, as this directly affects the efficiency of the panel. Only with a precise, fast and reliable inline measuring system can the production parameters be continuously monitored and, thus, the quality of the coating processes ensured.

A typical thin film photovoltaic (PV) system is comprised of a fairly complex stack of layers coated onto substrates like glass or foils. As manufacturers strive to develop lower-cost, dependable CdTe/CIS/CIGS products, some of their most critical issues are:

· ever-higher module efficiencies

· ever-thinner absorber layers of less than 1µm

· consistent absorber film stoichiometry and uniformity over large areas

This is where mature, non-destructive measurement technology, such as X-ray fluorescence (XRF), helps to improve uniformity and stoichiometry – and thus, the cell efficiency and production yield. The FISCHERSCOPE® X-RAY 5400 enables accurate and precise measure­ment of the layer thicknesses and composition in complex CIS/CIGS/CdTe systems, for continuous inline quality control at various stages during production.

Fig.1: X-ray head of a FISCHERSCOPE® X-RAY 5400 (left) and detailed view of the easy-to-change protective foil

Because the X-ray heads are mounted via cooled standard interfaces to the vacuum chamber system, they can even be used in production machinery under condi­tions in which substrate temperatures approach 500°C.

Movement and bulging of the product can occur during the production process, which causes the distance between sample and measurement head to fluctuate. To prevent falsifying effects, FISCHER’s WinFTM® Software uses information already contained in the measured XRF spectra, achieving reliable distance compensation without any moving parts and thus obviating the need for secondary distance sensors.

With the distance compensation feature activated, the measurement distance can be altered by up to +/- 5 mm without significantly affecting the measurement readings.

Production quality of thin film solar cells can be accurately and precisely monitored using XRF technology. FISCHER’s specially designed inline X-ray measurement head, FISCHERSCOPE® X-RAY 5400, also fulfils all the robustness requirements of live production environments. For more information please contact your local FISCHER representative.